Semiconductor device

ABSTRACT

According to one embodiment, a semiconductor device includes first to third electrodes, a semiconductor member, a first conductive member, first and second insulating members, and a first nitride member. A position of the third electrode in a first direction from the first to second electrodes is between positions of the first and second electrodes in the first direction. The semiconductor member includes first and second semiconductor regions. The first semiconductor region includes first to fifth partial regions. The second semiconductor region includes first and second semiconductor portions. The second semiconductor portion includes first and second portions, and a third portion between the first and second portions. The first conductive member includes first and second conductive regions. The first insulating member includes a first insulating region. The second insulating member includes first and second insulating portions. The first nitride member includes a first nitride region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2021-139068, filed on Aug. 27, 2021, andJapanese Patent Application No. 2022-000057, filed on Jan. 4, 2022; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein generally relate to a semiconductor device.

BACKGROUND

For example, there is a semiconductor device using a nitridesemiconductor. Improvement of characteristics is desired insemiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a semiconductordevice according to a first embodiment;

FIG. 2 is a schematic cross-sectional view illustrating a semiconductordevice according to the first embodiment;

FIG. 3 is a schematic cross-sectional view illustrating a semiconductordevice according to a second embodiment;

FIG. 4 is a schematic cross-sectional view illustrating a semiconductordevice according to the second embodiment;

FIG. 5 is a schematic cross-sectional view illustrating a semiconductordevice according to a third embodiment; and

FIG. 6 is a schematic cross-sectional view illustrating a semiconductordevice according to the third embodiment.

DETAILED DESCRIPTION

According to one embodiment, a semiconductor device includes a firstelectrode, a second electrode, a third electrode, a semiconductormember, a first conductive member, a first insulating member, a secondinsulating member, and a first nitride member. A position of the thirdelectrode in a first direction from the first electrode to the secondelectrode is between a position of the first electrode in the firstdirection and a position of the second electrode in the first direction.The semiconductor member includes a first semiconductor region and asecond semiconductor region. The first semiconductor region includesAl_(x1)Ga_(1-x1)N (0≤x1<1). The first semiconductor region includes afirst partial region, a second partial region, a third partial region, afourth partial region, and a fifth partial region. A second directionfrom the first partial region to the first electrode crosses the firstdirection. A direction from the second partial region to the secondelectrode is along the second direction. A direction from the thirdregion to the third electrode is along the second direction. A positionof the fourth partial region in the first direction is between aposition of the first partial region in the first direction and aposition of the third partial region in the first direction. A positionof the fifth partial region in the first direction is between theposition of the third partial region in the first direction and aposition of the second partial region in the first direction. The secondsemiconductor region includes Al_(x2)Ga_(1-x2)N (0≤x2≤1, x1<x2). Thesecond semiconductor region includes a first semiconductor portion and asecond semiconductor portion. A direction from the fourth partial regionto the first semiconductor portion is along the second direction. Adirection from the fifth partial region to the second semiconductorportion is along the second direction. The second semiconductor portionincludes a first portion, a second portion, and a third portion betweenthe first portion and the second portion. A position of the secondportion in the first direction is between a position of the firstportion in the first direction and the position of the second electrodein the first direction. The first conductive member includes a firstconductive region and a second conductive region. The first conductiveregion overlaps the third electrode in the second direction. The firstportion is between the fifth partial region and a part of the firstconductive region. The first conductive member is electrically connectedwith one of the first electrode and the third electrode, or the firstconductive member is configured to be electrically connected with theone of the first electrode and the third electrode. The first insulatingmember includes a first insulating region. The first insulating regionis between the third partial region and the third electrode in thesecond direction. The second insulating member includes a firstinsulating portion and a second insulating portion. The first insulatingportion is between the first portion and the first conductive region inthe second direction. The second portion is between the fifth partialregion and the second insulating portion. The first nitride memberincludes Al_(x3)Ga_(1-x3)N (0≤x3<1) or In_(y1)Al_(y2)Ga_(1-y1-y2)N(0<y1≤1, 0≤y2≤1, y1+y2≤1). The first nitride member includes a firstnitride region. The first nitride region is between the first insulatingportion and the second insulating portion in the first direction. Thefirst nitride region is between the third portion and the secondconductive region in the second direction.

Various embodiments are described below with reference to theaccompanying drawings.

The drawings are schematic and conceptual; and the relationships betweenthe thickness and width of portions, the proportions of sizes amongportions, etc., are not necessarily the same as the actual values. Thedimensions and proportions may be illustrated differently amongdrawings, even for identical portions.

In the specification and drawings, components similar to those describedpreviously or illustrated in an antecedent drawing are marked with likereference numerals, and a detailed description is omitted asappropriate.

First embodiment

FIG. 1 is a schematic cross-sectional view illustrating a semiconductordevice according to a first embodiment.

As shown in FIG. 1 , a semiconductor device 110 according to theembodiment includes a first electrode 51, a second electrode 52, a thirdelectrode 53, a semiconductor member 10M, a first conductive member 61,a first insulating member 41, and a second insulating member 42.

A direction from the first electrode 51 to the second electrode 52 is afirst direction D1. The first direction D1 is defined as an X-axisdirection. One direction perpendicular to the X-axis direction isdefined as a Z-axis direction. The direction perpendicular to the X-axisdirection and the Z-axis direction is defined as a Y-axis direction.

A position of the third electrode 53 in the first direction D1 isbetween a position of the first electrode 51 in the first direction D1and a position of the second electrode 52 in the first direction D1. Forexample, at least a part of the third electrode 53 is located betweenthe first electrode 51 and the second electrode 52 in the firstdirection D1.

The semiconductor member 10M includes a first semiconductor region 10and a second semiconductor region 20. In this example, the semiconductordevice 110 includes a base body 10 s and a nitride semiconductor layer10B. The nitride semiconductor layer 10B is provided between the basebody 10 s and the semiconductor member 10M. For example, the nitridesemiconductor layer 10B is provided on the base body 10 s. Thesemiconductor member 10M is provided on the nitride semiconductor layer10B. For example, the first semiconductor region 10 is provided on thenitride semiconductor layer 10B. The second semiconductor region 20 isprovided on the first semiconductor region 10. The first to thirdelectrodes 51 to 53 are provided on the semiconductor member 10M. Thebase body 10 s may be, for example, a silicon substrate or a SiCsubstrate. The nitride semiconductor layer 10B includes, for example,AlGaN.

The first semiconductor region 10 includes Al_(x1)Ga_(1-x1)N (0≤x1<1).The first semiconductor region 10 is, for example, a GaN layer. Thecomposition ratio x1 of Al in the first semiconductor region 10 may be,for example, not less than 0 and not more than 0.1.

For example, the first semiconductor region 10 includes GaN. The firstsemiconductor region 10 includes a first partial region 11, a secondpartial region 12, a third partial region 13, a fourth partial region14, and a fifth partial region 15. The second direction D2 from thefirst partial region 11 to the first electrode 51 crosses the firstdirection D1. The second direction D2 may be, for example, the Z-axisdirection.

A direction from the second partial region 12 to the second electrode 52is along the second direction D2. A direction from the third partialregion 13 to the third electrode 53 is along the second direction D2.

A portion of the first semiconductor region 10 that overlaps the firstelectrode 51 in the second direction D2 corresponds to the first partialregion 11. A portion of the first semiconductor region 10 that overlapsthe second electrode 52 in the second direction D2 corresponds to thesecond portion region 12. A portion of the first semiconductor region 10that overlaps the third electrode 53 in the second direction D2corresponds to the third portion region 13.

A position of the fourth partial region 14 in the first direction D1 isbetween a position of the first partial region 11 in the first directionD1 and a position of the third partial region 13 in the first directionD1. A position of the fifth partial region 15 in the first direction D1is between a position of the third partial region 13 in the firstdirection D1 and a position of the second partial region 12 in the firstdirection D1. The first to fifth subregions 11 to 15 may be continuouswith each other. The boundaries between the first to fifth subregions 11to 15 may be clear or unclear.

The second semiconductor region 20 includes Al_(x2)Ga_(1-x2)N (0<x2≤1,x1<x2). The second semiconductor region 20 is, for example, an AlGaNlayer. The composition ratio x2 of Al in the second semiconductor region20 may be, for example, not less than 0.25 and not more than 0.4.

The second semiconductor region 20 includes a first semiconductorportion 21 and the second semiconductor portion 22. A direction from thefourth partial region 14 to the first semiconductor portion 21 is alongthe second direction D2. A direction from the fifth partial region 15 tothe second semiconductor portion 22 is along the second direction D2.The second semiconductor portion 22 includes a first portion 22 a, asecond portion 22 b, and a third portion 22 c. The third portion 22 c isbetween the first portion 22 a and the second portion 22 b. A positionof the second portion 22 b in the first direction D1 is between aposition of the first portion 22 a in the first direction D1 and theposition of the second electrode 52 in the first direction D1. The firstto third portions 22 a to 22 c may be continuous with each other. Theboundary between the first to third portions 22 a to 22 c may be clearor unclear.

For example, the first electrode 51 is electrically connected with thefirst semiconductor portion 21. For example, the second electrode 52 iselectrically connected with the second semiconductor portion 22.

The first conductive member 61 includes a first conductive region 61 aand a second conductive region 61 b. The first conductive region 61 aoverlaps the third electrode 53 in the second direction D2. The secondconductive region 61 b does not overlap the third electrode 53 in thesecond direction D2. A position of the second conductive region 61 b inthe first direction D1 is between the position of the third electrode 53in the first direction D1 and the position of the second electrode 52 inthe first direction D1. The second conductive region 61 b corresponds toa protruding portion protruding toward a side of the second electrode 52with reference to the third electrode 53. The second conductive region61 b corresponds to, for example, the eaves.

The first portion 22 a is located between the fifth partial region 15and a part of the first conductive region 61 a in the second directionD2. In this example, the third electrode 53 is located between the fifthpartial region 15 and the first conductive region 61 a in the seconddirection D2. At least a part of the second portion 22 b does notoverlap the first conductive member 61 in the second direction D2.

In the embodiment, the first conductive member 61 is electricallyconnected with one of the first electrode 51 and the third electrode 53.Alternatively, the first conductive member 61 is configured to beelectrically connect with one of the first electrode 51 and the thirdelectrode 53. In the first embodiment, the first conductive member 61 iselectrically connected with the first electrode 51. A terminalelectrically connected with the first conductive member 61 and aterminals electrically connected with the first electrode 51 may beprovided, and these terminals may be electrically connected when thesemiconductor device is used.

For example, the first conductive member 61 includes a first conductiveend portion 61 e. The first conductive end portion 61 e is an end on theside of the second electrode 52 in the first direction D1. A position ofthe first conductive end portion 61 e in the first direction D1 isbetween the position of the third electrode 53 in the first direction D1and the position of the second electrode 52 in the first direction D1.

The first insulating member 41 includes a first insulating region 41 a.The first insulating region 41 a is located between the third partialregion 13 and the third electrode 53 in the second direction D2.

The second insulating member 42 includes a first insulating portion 42 aand a second insulating portion 42 b. The first insulating portion 42 ais located between the first portion 22 a and the first conductiveregion 61 a in the second direction D2. The second portion 22 b isbetween the fifth portion region 15 and the second insulating portion 42b.

The first nitride member 31 includes Al_(x3)Ga_(1-x3)N (0≤x3<1). Thefirst nitride member 31 is, for example, a GaN layer or an AlGaN layer.The composition ratio x3 of Al in the first nitride member 31 may be,for example, not less than 0 and not more than 0.5. For example, thecomposition ratio x3 of Al in the first nitride member 31 is lower thanthe composition ratio x2 of Al in the second semiconductor region 20(for example, the second semiconductor portion 22).

The first nitride member 31 includes a first nitride region 31 a. Thefirst nitride region 31 a is located between the first insulatingportion 42 a and the second insulating portion 42 b in the firstdirection D1. The first nitride region 31 a is between the third portion22 c and the second conductive region 61 b in the second direction D2.The first nitride region 31 a overlaps the second conductive region 61 bin the second direction D2.

A current flowing between the first electrode 51 and the secondelectrode 52 can be controlled by a potential of the third electrode 53.The potential of the third electrode 53 may be, for example, a potentialbased on a potential of the first electrode 51. For example, the firstelectrode 51 functions as a source electrode. The second electrode 52functions as a drain electrode. The third electrode 53 functions as agate electrode. The first insulating region 41 a functions as a gateinsulating film. The semiconductor device 110 is, for example, atransistor. For example, a distance between the first electrode 51 andthe third electrode 53 is shorter than a distance between the thirdelectrode 53 and the second electrode 52.

A carrier region 10C is formed in a portion of the first semiconductorregion 10 facing the second semiconductor region 20. The carrier region10C is, for example, a two-dimensional electron gas. The semiconductordevice 110 is, for example, a HEMT (high electron mobility transistor).

The first conductive member 61 functions as, for example, a field plate.As described above, in the embodiment, the first conductive member 61 isprovided with the second conductive region 61 b (protruding portion oreaves portion). The first nitride region 31 a (GaN or AlGaN) is providedat a position overlapping the second conductive region 61 b. As aresult, the carrier concentration in the carrier region 10C locallydecreases in the region overlapping the second conductive region 61 b.

Generally, the electric field is concentrated at the end (firstconductive end 61 e) of the second conductive region 61 b (protrudingportion or eaves). The breakdown voltage tends to decrease due to theconcentration of the electric field. In the embodiment, the carrierconcentration can be locally reduced in the region overlapping thesecond conductive region 61 b. As a result, high breakdown voltage canbe easily obtained. According to the embodiment, it is possible toprovide a semiconductor device whose characteristics can be improved.

In this example, the first nitride member 31 includes a second nitrideregion 31 b and a third nitride region 31 c. The first insulatingportion 42 a is between the first portion 22 a and the second nitrideregion 31 b. The second insulating portion 42 b is between the secondportion 22 b and the third nitride region 31 c. The first nitride region31 a, the second nitride region 31 b, and the third nitride region 31 cmay be continuous with each other. The boundaries between the firstnitride region 31 a, the second nitride region 31 b, and the thirdnitride region 31 c may be clear or unclear. By continuously providingthe first nitride region 31 a, the second nitride region 31 b, and thethird nitride region 31 c, the formation of the first nitride member 31is easy.

A portion of the first nitride member 31 that overlaps the secondconductive region 61 b in the second direction D2 corresponds to thefirst nitride region 31 a. In the first nitride member 31, a portionbetween the first insulating portion 42 a and the second insulatingportion 42 b in the first direction D1 corresponds to the first nitrideregion 31 a. In this example, the first nitride region 31 a is incontact with the third portion 22 c. As will be described later, anotherlayer (for example, an AlN layer) may be provided between the firstnitride region 31 a and the third portion 22 c.

For example, the crystallinity of the first nitride region 31 a may behigher than the crystallinity of the second nitride region 31 b and maybe higher than the crystallinity of the third nitride region 31 c. Atleast a part of the first nitride region 31 a may include crystals. Atleast a part of the second nitride region 31 b may be amorphous. Atleast a part of the third nitride region 31 c may be amorphous.

The thickness t1 of the first nitride region 31 a along the seconddirection D2 is, for example, not less than 1 nm and not more than 10nm. When the thickness t1 is not less than 1 nm, for example, ahomogeneous first nitride region 31 a can be easily obtained. When thethickness t1 is not more than 10 nm, it is easy to suppress crystaldefects such as misfit dislocations caused by film stress, for example.The thickness t1 may be not less than 3 nm and not more than 5 nm. Whenthe thickness t1 is not less than 3 nm, for example, a homogeneous firstnitride region 31 a can be more easily obtained. When the thickness t1is not less than 3 nm, for example, the carrier concentration can bestably controlled. When the thickness t1 is not mor than 5 nm, it iseasier to suppress crystal defects such as misfit dislocations caused byfilm stress, for example.

In the embodiment, the second insulating member 42 includes silicon andnitrogen. The second insulating member 42 includes, for example, SiN.With such a second insulating member 42, high quality can be easilyobtained in the semiconductor member 10M under the second insulatingmember 42.

For example, the first insulating member 41 includes silicon and oxygen.The first insulating member 41 includes, for example, silicon oxide(SiO₂). For example, the first insulating member 41 does not nitrogensubstantially. Alternatively, the concentration of nitrogen in the firstinsulating member 41 is lower than the concentration of nitrogen in thesecond insulating member 42. With such a first insulating member 41, forexample, a stable threshold voltage can be easily obtained.

As shown in FIG. 1 , the first insulating member 41 may further includea second insulating region 41 b and a third insulating region 41 c. Thesecond insulating region 41 b is located between the first semiconductorportion 21 and the third electrode 53 in the first direction D1. Thethird insulating region 41 c is located between the third electrode 53and the second semiconductor portion 22 in the first direction D1. Atleast a part of the third electrode 53 is between the firstsemiconductor portion 21 and the second semiconductor portion 22 in thefirst direction D1.

At least a part of the first insulation region 41 a is between thefourth partial region 14 and the fifth partial region 15 in the firstdirection D1. For example, the semiconductor member 10M is provided witha recess, and at least a part of the third electrode 53 is filled in therecess. The semiconductor device 110 is a gate recess type transistor.

As shown in FIG. 1 , the second insulating member 42 may include a thirdinsulating portion 42 c. The first semiconductor portion 21 is betweenthe fourth portion region 14 and the third insulating portion 42 c.

As shown in FIG. 1 , the first insulating member 41 further includes afourth insulating region 41 d. At least a part of the fourth insulatingregion 41 d is between the third electrode 53 and the first conductivemember 61.

The first insulating member 41 may include a fifth insulating region 41e and a sixth insulating region 41 f. The first semiconductor portion 21is between the fourth partial region 14 and the fifth insulating region41 e. The second semiconductor portion 22 is between the fifth portionregion 15 and the sixth insulating region 41 f.

As shown in FIG. 1 , a length of the first nitride region 31 a along thefirst direction D1 is defined as a first length w1. The secondsemiconductor portion 22 includes an end 22 p on the side of the thirdelectrode 53. The second semiconductor portion 22 includes a portion 22q that overlaps the second electrode 52 in the second direction D2. Adistance in the first direction D1 between the end 22 p on the side ofthe third electrode 53 of the second semiconductor portion 22 and theposition of the portion 22 q of the second semiconductor portion 22 thatoverlaps the second electrode 52 in the second direction D2 is definedas a second length w2. The first length w1 is, for example, note lessthan 0.035 times and not more than 0.5 times the second length w2. Withsuch a first length w1, for example, a region in which the carrierconcentration is controlled is appropriately formed, and a highbreakdown voltage can be effectively obtained.

FIG. 2 is a schematic cross-sectional view illustrating a semiconductordevice according to the first embodiment.

As shown in FIG. 2 , a semiconductor device 111 according to theembodiment includes a second nitride member 32. Except for this, theconfiguration of the semiconductor device 111 is the same as theconfiguration of the semiconductor device 110. For example, in thesemiconductor device 111, the configurations of the first electrode 51,the second electrode 52, the third electrode 53, the semiconductormember 10M, the first conductive member 61, the first insulating member41, the second insulating member 42, and the first nitride member 31 maybe the same as those in the semiconductor device 110.

The second nitride member 32 includes Al_(x4)Ga_(1-x4)N (0<x4≤1, x3<x4).The second nitride member 32 may be, for example, an AlN layer. Thecomposition ratio x4 of Al in the second nitride member 32 may be, forexample, not less than 0.5 and not more than 1.0.

At least a part of the second nitride member 32 is between the firstportion 22 a and the first insulating portion 42 a, and between thesecond portion 22 b and the second insulating portion 42 b. A part ofthe second nitride member 32 may be provided between the third portion22 c and the first nitride region 31 a.

By providing the second nitride member 32 as described above, highquality can be obtained in the second semiconductor portion 22. Forexample, damage to the second semiconductor portion 22 by the secondinsulating member 42 can be suppressed.

Also in the semiconductor device 111, the carrier concentration can belocally reduced in the region overlapping the second conductive region61 b. High breakdown voltage is easy to obtain. It is possible toprovide a semiconductor device whose characteristics can be improved.

For example, the second nitride member 32 may be in contact with thethird portion 22 c and the first nitride region 31 a.

As shown in FIG. 2 , a part of the second nitride member 32 may beprovided between the first semiconductor portion 21 and the thirdinsulating portion 42 c. For example, damage to the second semiconductorportion 22 by the second insulating member 42 can be suppressed.

The thickness t2 of the second nitride member 32 along the seconddirection D2 is, for example, not less than 1 nm and not more than 10nm. When the thickness t2 is not less than 1 nm, for example, damage tothe second semiconductor region 20 can be effectively suppressed. Whenthe thickness t2 is not more than 10 nm, for example, in the secondnitride member 32, it is easy to suppress crystal defects such as misfitdislocations due to film stress. The thickness t2 may be, for example,not less than 3 nm and not more than 5 nm. When the thickness t2 is notless than 3 nm, damage to the second semiconductor region 20 can besuppressed more effectively. When the thickness t2 is not more than 5nm, it is easier to suppress crystal defects such as misfit dislocationsdue to film stress.

Second Embodiment

FIG. 3 is a schematic cross-sectional view illustrating a semiconductordevice according to a second embodiment.

As shown in FIG. 3 , in a semiconductor device 112 according to theembodiment, the first conductive member 61 is electrically connectedwith the third electrode 53. Except for this, the configuration of thesemiconductor device 112 is the same as the configuration of thesemiconductor device 110. For example, in the semiconductor device 112,the configuration of the first electrode 51, the second electrode 52,the third electrode 53, the semiconductor member 10M, the firstinsulating member 41, the second insulating member 42, and the firstnitride member 31 may be the same as those in the semiconductor device110.

In the semiconductor device 112, a terminal electrically connected withthe first conductive member 61 and a terminal electrically connectedwith the third electrode 53 are provided, and these terminals may beelectrically connected when the semiconductor device is used.

The first nitride region 31 a is also provided in the semiconductordevice 112. The first nitride region 31 a is located between the firstinsulating portion 42 a and the second insulating portion 42 b in thefirst direction D1. The first nitride region 31 a is between the thirdportion 22 c and the second conductive region 61 b in the seconddirection D2. The first nitride region 31 a overlaps the secondconductive region 61 b in the second direction D2.

As a result, the carrier concentration in the carrier region 10C locallydecreases in the region overlapping the second conductive region 61 b.As a result, high breakdown voltage can be easily obtained. According tothe embodiment, it is possible to provide a semiconductor device whosecharacteristics can be improved.

FIG. 4 is a schematic cross-sectional view illustrating a semiconductordevice according to the second embodiment.

As shown in FIG. 4 , a semiconductor device 113 according to theembodiment includes the second nitride member 32. Except for this, theconfiguration of the semiconductor device 113 is the same as theconfiguration of the semiconductor device 112. For example, in thesemiconductor device 113, the configurations of the first electrode 51,the second electrode 52, the third electrode 53, the semiconductormember 10M, the first conductive member 61, the first insulating member41, the second insulating member 42, and the first nitride member 31 maybe the same as those in the semiconductor device 112.

Also in the semiconductor device 113, the carrier concentration can belocally lowered in the region overlapping the second conductive region61 b. High breakdown voltage is easy to obtain. It is possible toprovide a semiconductor device whose characteristics can be improved.

In the embodiment, information on crystallinity can be obtained, forexample, by an X-ray diffraction pattern image. Information on thecomposition ratio can be obtained by, for example, X-ray photoelectronspectroscopy.

Un the semiconductor devices 110 to 113 according to the embodiment, thefirst nitride member 31 may include In, Ga and nitrogen. For example,the first nitride member 31 may include Al_(x3)Ga_(1-x3)N (0≤x3<1) orIn_(y1)Al_(y2)Ga_(1-y1-y2)N (0<y1≤1, 0≤y2<1, y1+y2≤1). For example, thefirst nitride member 31 may include In_(y1)Ga_(1-y1)N (0<y1≤1). On theother hand, the second nitride member 32 includes Al_(x4)Ga_(1-x4)N(0<x4≤1, x3<x4). For example, the first nitride member 31 includesInGaN, and the second nitride member 32 includes AlGaN or AlN.

Third Embodiment

FIG. 5 is a schematic cross-sectional view illustrating a semiconductordevice according to a third embodiment.

As shown in FIG. 5 , in a semiconductor device 121, the first nitridemember 31 includes fourth to seventh nitride regions 31 d to 31 g inaddition to the first to third nitride regions 31 a to 31 c. The secondnitride member 32 includes first to seventh nitride portions 32 a to 32g.

The first nitride portion 32 a is between the third portion 22 c and thefirst nitride region 31 a. The second nitride portion 32 b is betweenthe first portion 22 a and the second nitride region 31 b. The thirdnitride portion 32 c is between the second portion 22 b and the thirdnitride region 31 c.

The fourth nitride region 31 d is located between the third partialregion 13 and the third electrode 53 in the second direction D2. Thefifth nitride region 31 e is, for example, between the firstsemiconductor portion 21 and at least a part of the third electrode 53in the first direction D1. The fifth nitride region 31 e is, forexample, between the first semiconductor portion 21 and at least a partof the second insulating region 41 b in the first direction D1. Thesixth nitride region 31 f is, for example, between at least a part ofthe third electrode 53 and the first portion 22 a in the first directionD1. The sixth nitride region 31 f is, for example, between at least apart of the third insulating region 41 c and the first portion 22 a inthe first direction D1.

The fourth nitride portion 32 d is located between the third partialregion 13 and the fourth nitride region 31 d in the second direction D2.The fifth nitride portion 32 e is located between the firstsemiconductor portion 21 and the fifth nitride region 31 e in the seconddirection D2. The sixth nitride portion 32 f is located between thesixth nitride region 31 f and the first portion 22 a in the seconddirection D2.

The first semiconductor portion 21 is located between the fourth partialregion 14 and the seventh nitride region 31 g in the second directionD2. The third insulating portion 42 c is located between the seventhnitride portion 32 g and the seventh nitride region 31 g in the seconddirection D2.

The configuration of the semiconductor device 121 other than the abovemay be the same as that of the semiconductor device 111. By providingthe first nitride member 31 and the second nitride member 32 asdescribed above, for example, a lower subthreshold swing can be easilyobtained.

FIG. 6 is a schematic cross-sectional view illustrating a semiconductordevice according to the third embodiment.

As shown in FIG. 6 , in a semiconductor device 122, the first nitridemember 31 includes the first to seventh nitride regions 31 a to 31 g.The second nitride member 32 includes the first to seventh nitrideportions 32 a to 32 g. The configuration of the semiconductor device 122other than the above may be the same as that of the semiconductor device112. By providing the first nitride member 31 and the second nitridemember 32 as described above, for example, a lower subthreshold swingcan be easily obtained.

In the semiconductor devices 112 and 122, for example, the first nitridemember 31 may include Al_(x3)Ga_(1-x3)N (0≤x3<1) orIn_(y1)Al_(y2)Ga_(1-y1-y2)N (0<y1≤1, 0≤y2≤1, y1+y2≤1). For example, thefirst nitride member 31 may include In_(y1)Ga_(1-y1)N (0<y1≤1). On theother hand, the second nitride member 32 includes Al_(x4)Ga_(1-x4)N(0<x4≤1, x3<x4). For example, the first nitride member 31 includesInGaN, and the second nitride member 32 includes AlGaN or AlN.

According to the embodiments, it is possible to provide a semiconductordevice whose characteristics can be improved.

In the specification, “nitride semiconductor” includes all compositionsof semiconductors of the chemical formula B_(x)In_(y)Al_(z)Ga_(1-x-y-z)N(0≤x≤1, 0≤y≤1, 0≤z≤1, and x+y+z≤1) for which the composition ratios x,y, and z are changed within the ranges respectively. “Nitridesemiconductor” further includes group V elements other than N (nitrogen)in the chemical formula recited above, various elements added to controlvarious properties such as the conductivity type and the like, andvarious elements included unintentionally.

In the specification of the application, “perpendicular” and “parallel”refer to not only strictly perpendicular and strictly parallel but alsoinclude, for example, the fluctuation due to manufacturing processes,etc. It is sufficient to be substantially perpendicular andsubstantially parallel.

Hereinabove, exemplary embodiments of the invention are described withreference to specific examples. However, the embodiments of theinvention are not limited to these specific examples. For example, oneskilled in the art may similarly practice the invention by appropriatelyselecting specific configurations of components included insemiconductor devices such as electrodes semiconductor members, compoundmembers, nitride members, insulating members, etc., from known art. Suchpractice is included in the scope of the invention to the extent thatsimilar effects thereto are obtained.

Further, any two or more components of the specific examples may becombined within the extent of technical feasibility and are included inthe scope of the invention to the extent that the purport of theinvention is included.

Moreover, all semiconductor devices practicable by an appropriate designmodification by one skilled in the art based on the semiconductordevices described above as embodiments of the invention also are withinthe scope of the invention to the extent that the purport of theinvention is included.

Various other variations and modifications can be conceived by thoseskilled in the art within the spirit of the invention, and it isunderstood that such variations and modifications are also encompassedwithin the scope of the invention.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. A semiconductor device, comprising: a firstelectrode; a second electrode; a third electrode, a position of thethird electrode in a first direction from the first electrode to thesecond electrode being between a position of the first electrode in thefirst direction and a position of the second electrode in the firstdirection; a semiconductor member including a first semiconductor regionand a second semiconductor region, the first semiconductor regionincluding Al_(x1)Ga_(1-x1)N (0≤x1<1), the first semiconductor regionincluding a first partial region, a second partial region, a thirdpartial region, a fourth partial region, and a fifth partial region, asecond direction from the first partial region to the first electrodecrossing the first direction, a direction from the second partial regionto the second electrode being along the second direction, a directionfrom the third region to the third electrode being along the seconddirection, a position of the fourth partial region in the firstdirection being between a position of the first partial region in thefirst direction and a position of the third partial region in the firstdirection, a position of the fifth partial region in the first directionbeing between the position of the third partial region in the firstdirection and a position of the second partial region in the firstdirection; the second semiconductor region including Al_(x2)Ga_(1-x2)N(0<x2≤1, x1<x2), the second semiconductor region including a firstsemiconductor portion and a second semiconductor portion, a directionfrom the fourth partial region to the first semiconductor portion beingalong the second direction, a direction from the fifth partial region tothe second semiconductor portion being along the second direction, thesecond semiconductor portion including a first portion, a secondportion, and a third portion between the first portion and the secondportion, a position of the second portion in the first direction beingbetween a position of the first portion in the first direction and theposition of the second electrode in the first direction; a firstconductive member including a first conductive region and a secondconductive region, the first conductive region overlapping the thirdelectrode in the second direction, the first portion being between thefifth partial region and a part of the first conductive region, thefirst conductive member being electrically connected with one of thefirst electrode and the third electrode, or the first conductive memberbeing configured to be electrically connected with the one of the firstelectrode and the third electrode; a first insulating member including afirst insulating region, the first insulating region being between thethird partial region and the third electrode in the second direction; asecond insulating member including a first insulating portion and asecond insulating portion, the first insulating portion being betweenthe first portion and the first conductive region in the seconddirection, the second portion being between the fifth partial region andthe second insulating portion; and a first nitride member includingAl_(x3)Ga_(1-x3)N (0≤x3<1) or In_(y1)Al_(y2)Ga_(1-y1-y2)N (0<y1≤0≤y2≤1,y1+y2≤1), the first nitride member including a first nitride region, thefirst nitride region being between the first insulating portion and thesecond insulating portion in the first direction, the first nitrideregion being between the third portion and the second conductive regionin the second direction.
 2. The device according to claim 1, wherein atleast a part of the second insulating portion does not overlap the firstconductive member in the second direction.
 3. The device according toclaim 1, wherein the first nitride member further includes a secondnitride region and a third nitride region, the first insulating portionis between the first portion and the second nitride region, and thesecond insulating portion is between the second portion and the thirdnitride region.
 4. The device according to claim 3, wherein acrystallinity of the first nitride region is higher than a crystallinityof the second nitride region and higher than a crystallinity of thethird nitride region.
 5. The device according to claim 3, wherein atleast a part of the first nitride region includes a crystal, at least apart of the second nitride region is amorphous, and at least a part ofthe third nitride region is amorphous.
 6. The device according to claim1, wherein the first nitride region is in contact with the thirdportion.
 7. The device according to claim 1, further comprising a secondnitride member including Al_(x4)Ga_(1-x4)N (0<x4≤1, x3<x4), at least apart of the second nitride member being between the first portion andthe first insulating portion, and between the second portion and thesecond insulating portion.
 8. The device according to claim 7, wherein apart of the second nitride member is between the third portion and thefirst nitride region.
 9. The device according to claim 7, wherein thesecond nitride member is in contact with the third portion and the firstnitride region.
 10. The device according to claim 7, wherein a thicknessof the second nitride member along the second direction is not less than1 nm and not more than 10 nm.
 11. The device according to claim 1,wherein the x3 is lower than the x2.
 12. The device according to claim1, wherein a thickness of the first nitride region along the seconddirection is not less than 1 nm and not more than 10 nm.
 13. The deviceaccording to claim 1, wherein the second insulating member includessilicon and nitrogen.
 14. The device according to claim 13, wherein thefirst insulating member includes silicon and oxygen, the firstinsulating member does not include nitrogen or a concentration ofnitrogen in the first insulating member is lower than a concentration ofnitrogen in the second insulating member.
 15. The device according toclaim 1, wherein the first insulating member further includes a secondinsulating region and a third insulating region, the second insulatingregion is between the first semiconductor portion and the thirdelectrode in the first direction, and the third insulating region isbetween the third electrode and the second semiconductor portion in thefirst direction.
 16. The device according to claim 1, wherein the firstinsulating member further includes a fourth insulating region, and atleast a part of the fourth insulating region is between the thirdelectrode and the first conductive member.
 17. The device according toclaim 1, wherein at least a part of the first insulating region isbetween the fourth partial region and fifth partial region in the firstdirection.
 18. The device according to claim 1, wherein at least a partof the third electrode is between the first semiconductor portion andthe second semiconductor portion in the first direction.
 19. The deviceaccording to claim 1, wherein a distance between the first electrode andthe third electrode along the first direction is shorter than a distancebetween the third electrode and the second electrode along the firstdirection.
 20. The device according to claim 1, wherein a first lengthof the first nitride region along the first direction is not less than0.035 times and not more than 0.5 times a second length, and the secondlength is a distance in the first direction between an end of the secondsemiconductor portion on a side of the third electrode and a position ofa portion of the second semiconductor portion that overlaps the secondelectrode in the second direction.